Playability and decorative upgrades

Major improvement is a work-around for play on touch-screen devices.  Code now just throws away spurious extra unintended touch events that I couldn't find a better way to eliminate. 

Other "decorative" enhancements:  

changed the word pictures to building blocks when they are added to the "factory" building. 

added very crude fireworks when the building is complete (and at the same time the construction equipment and work site disappears.)

and a few other minor things. . . .